# Problem: large single index with mmap

**URL:** https://discuss.elastic.co/t/problem-large-single-index-with-mmap/95585
**Category:** Elasticsearch
**Created:** [August 2, 2017, 5:25pm UTC](https://discuss.elastic.co/t/problem-large-single-index-with-mmap/95585 "2017-08-02T17:25:49Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![anks](https://avatars.discourse-cdn.com/v4/letter/a/f07891/32.png) [@anks](https://discuss.elastic.co/u/anks)
#### Post date: [August 2, 2017, 5:25pm UTC](https://discuss.elastic.co/t/problem-large-single-index-with-mmap/95585/1 "2017-08-02T17:25:49Z")

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I am getting higher execution time around 10 sec when running query with mmapfs index having 2 TB size.

But the same query with another index 2 TB store type niofs executes it within 1 second.

Is single large single index of store type mmap is a problem?

FYI, I am having 64-bit unix machine with high vm.max\_map\_count and 10 nodes 200 GB RAM allocated to ES across nodes.

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<div class="post-metadata">

### Author: ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)
#### Post date: [August 30, 2017, 5:26pm UTC](https://discuss.elastic.co/t/problem-large-single-index-with-mmap/95585/2 "2017-08-30T17:26:56Z")

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